1. Field of the Invention
The present invention relates to a support system for a power train of a vehicle, particularly, capable of reducing vibrations transmitted from a power train mounted to a vehicle to a vehicle body by increasing rigidity of a mount bracket which supports the power train on the vehicle body.
2. Description of the Related Art
In a some vehicle in which a transmission is coupled to an engine arranged transversely so as to support an engine and transmission on a vehicle body via a mount insulator (engine mount), a mount bracket which fixes the mount insulator on the side of the transmission to the transmission is split horizontally into two parts for the convenience of assembly.
An example of such a support system for a power train of a vehicle includes one shown in FIGS. 6 and 7, in which a power train 103 is composed of an engine 101 and a transmission 102, and the power train 103 is supported to the vehicle body through a mount insulator 105 of a support system 104.                The mount insulator 105 is provided with a outer cylindrical member (outer cylinder) 106, an elastic member 107 secured to an inner peripheral surface of the outer cylinder 106 and a shaft 108 disposed to a center of the elastic member 108. A coupling member (coupler) is connected to an end portion of the shaft 108 and an outer cylinder side mount member 109 is mounted to the outer periphery of the outer cylinder 106.        
A mount bracket 111 is coupled to a top portion of a transmission casing 110 of the transmission 102. The mount bracket 111 is coupled to the coupler on the shaft 108 of the mount insulator 105. The mount insulator 105 couples the outer cylinder side mount member 109 of the outer cylinder 106 to the vehicle body.
The mount bracket 111 which couples the mount insulator 105 to the transmission 102 includes a first mount bracket portion 112 which extends upward from the top of the transmission casing 110 and a second mount bracket portion 113 which is coupled to the coupler on the shaft 108 by extending horizontally from an upper end portion of the first mount bracket portion 112.
The first mount bracket portion 112 includes a first vertical wall portion 115 and a second vertical wall portion 116 in a manner such that the first vertical wall portion 115 extends in a front-rear direction of the vehicle (i.e., longitudinal direction of the vehicle body) along a side portion of a shift tower 114 so as to be apart from the shift tower 114 which is a projection projecting upward from the transmission casing 110 while the second vertical wall portion 116 intersects the first vertical wall portion 115 by extending in lateral direction of the vehicle body along a side portion of the shift tower 114.
A first fastening member 117 and a second fastening member 118 are formed in lower end portions of the first vertical wall portion 115 and the second vertical wall portion 116, respectively, and are coupled to the upper portion of the transmission casing 110. The second mount bracket portion 113 includes a horizontal wall portion 119, which is fastened to an upper end portion of the first mount bracket portion 112 and coupled to the coupler at an end portion of the shaft 108 of the mount insulator 105.
In a conventional support system of a power train of a vehicle, an elastic member is mounted on a mount bracket so as to elastically come into press contact with a surface to which a transmission fastening surface cannot be formed (seat-surface-non-forming portion). The elastic member prevents the mount bracket from falling onto the seat-surface-non-forming portion to increase the coupling rigidity to thereby prevent vibration and noise from causing, for example, as disclosed in a Patent Document 1 (Japanese Utility Model Laid-Open Publication No. 5-72543).
Furthermore, in another conventional support system for a power train of a vehicle, a first fastening member to be coupled to a drive system member and a second fastening member which obliquely intersects a travel direction of the drive system member are formed on a mount-side bracket fixed to a mount insulator, and a slope to be coupled to the second fastening member is formed on an engine-side bracket fixed to the drive system member to thereby suppress decreasing in natural frequency of the mount insulator and prevent the vibration and noise from increasing, for example, as disclosed in a Patent Document 2 (Japanese Patent Laid-Open Publication No. 6-122325).
In the support system 104 for the power train of the vehicle shown in FIGS. 6 and 7, since the shift tower 114 of the transmission 102 exists around the mount bracket 111, the first mount bracket portion 112 of the mount bracket 111 is constructed to have a clearance (i.e., a shape having an escape clearance) in order for the first vertical wall portion 115 and the second vertical wall portion 116 so as to avoid contacting to the shift tower 114. If the first mount bracket portion 112 needs to provide a clearance in this way, a portion to which the clearance is formed will lack strength and rigidity. As a result, a (hatched region in FIG. 7) of the first mount bracket portion 112, which is coupled to the second mount bracket portion 113, will vibrate as indicated by an arrow, and the vibration will be transmitted to the vehicle body, thus being inconvenient.
Conventionally, as a countermeasure to the lack of strength and rigidity, a material with high strength and high rigidity is used for forming the first mount bracket portion, or conventionally, the first mount bracket portion and second mount bracket portion are fastened by using a separate stiffener for reinforcement, which however provides the following disadvantages.
That is, when the material is changed, for example, from aluminum to cast iron, entire weight of the system increases and the material change resulted in cost increasing. On the other hand, when a stiffener is added, the number of parts or components is increased, resulting in cost increasing.